The present disclosure relates to an image processing device and method and, more particularly, to an image processing device and method that allow for stable creation of a background while adjusting to background changes.
A process for extracting an object that does not exist in a background image built in advance by comparing an input image supplied from a camera or other device and the background image is generally referred to as a background subtraction algorithm (refer, for example, to Japanese Patent Laid-Open Nos. 2009-31939, 2009-265827 and, 2009-69996).
In a background subtraction algorithm, the following hypotheses are made with respect to a background image depending on the situation to which the algorithm is applied:
Background values basically remain unchanged.
Changes in the background values fall within a given range.
Changes in the background values fall within a plurality of given ranges.
Changes in the background values can be predicted in one way or the other.
A background model statistically describes these hypotheses. Besides, a background image is obtained by processing background models in one way or the other and converting the background models into a form that can be compared with an input image (normal image data format).
Statistical distribution of a group of past input images is used to build background models. Therefore, it is preferred that the group of input images should be observed over a long period of time to stably distinguish between background and non-background.
Besides, when a practical usage environment is assumed, changes in the following are highly possible with respect to the above hypotheses:
Changes in lighting conditions (sunshine and indoor lighting)
Changes in background objects (e.g., a car enters an image frame and comes to a stop)
Changes in camera orientation
As a result, countermeasures against such changes are necessary.